Details

Updated kernel-rt packages that fix two security issues and various bugsare now available for Red Hat Enterprise MRG 2.1.

The Red Hat Security Response Team has rated this update as havingimportant security impact. Common Vulnerability Scoring System (CVSS) basescores, which give detailed severity ratings, are available for eachvulnerability from the CVE links in the References section.

The kernel-rt packages contain the Linux kernel, the core of any Linuxoperating system.

This update fixes the following security issues:

* When a set user ID (setuid) application is executed, certain personalityflags for controlling the application's behavior are cleared (that is, aprivileged application will not be affected by those flags). It was foundthat those flags were not cleared if the application was made privilegedvia file system capabilities. A local, unprivileged user could use thisflaw to change the behavior of such applications, allowing them to bypassintended restrictions. Note that for default installations, no applicationshipped by Red Hat for Red Hat Enterprise MRG is made privileged via filesystem capabilities. (CVE-2012-2123, Important)

* A flaw was found in the way the Linux kernel's journal_unmap_buffer()function handled buffer head states. On systems that have an ext4 filesystem with a journal mounted, a local, unprivileged user could use thisflaw to cause a denial of service. (CVE-2011-4086, Moderate)

This update also fixes the following bugs:

* The CAP_SYS_ADMIN check was missing from the dmesg_restrict feature.Consequently, an unprivileged and jailed root user could bypass thedmesg_restrict protection. This update adds CAP_SYS_ADMIN to bothdmesg_restrict and kptr_restrict, which only allows writing todmesg_restrict when root has CAP_SYS_ADMIN. (BZ#808271)

* Previously, the _copy_from_pages() function, which is used to copy data from the temporary buffer to the user-passed buffer, was passed the wrong size parameter when copying data. Consequently, if the user provided a buffer greater than PAGE_SIZE, the getxattr() syscalls were handled incorrectly. This update fixes _copy_from_pages() to use the ACL length, which uses a correctly-sized buffer. (BZ#753230)

* Some older versions of hardware or their software could not recognizecertain commands and would log messages for illegal or unsupported errorsthe driver could not properly handle. This bug has been fixed and no boguserror messages are now returned in the described scenario. (BZ#813892)

* Previously, the qla2x00_poll() function did the local_irq_save() callbefore calling qla24xx_intr_handler(), which had a spinlock. Sincespinlocks are sleepable in the real-time kernel, it is not allowed to callthem with interrupts disabled. This scenario produced error messages andcould cause a system deadlock. With this update, thelocal_irq_save_nort(flags) function is used to save flags without disablinginterrupts, which prevents potential deadlocks and removes the errormessages. (BZ#818220)

Users should upgrade to these updated packages, which correct these issues.The system must be rebooted for this update to take effect.

Solution

Before applying this update, make sure all previously-released erratarelevant to your system have been applied.

To install kernel packages manually, use "rpm -ivh [package]". Do notuse "rpm -Uvh" as that will remove the running kernel binaries fromyour system. You may use "rpm -e" to remove old kernels afterdetermining that the new kernel functions properly on your system.

749143 - CVE-2011-4086 kernel: jbd2: unmapped buffer with _Unwritten or _Delay flags set can lead to DoS806722 - CVE-2012-2123 kernel: fcaps: clear the same personality flags as suid when fcaps are used818220 - qla2xxx does a spinlock with interrupts disabled